ICU · Infection / pharmacology
MDR Organisms — MRSA, VRE, ESBL, CRE & C. difficile
Also known as Multidrug-resistant organism · MDRO · MRSA · VRE · Vancomycin-resistant enterococcus · ESBL · Extended-spectrum beta-lactamase · CRE · Carbapenem-resistant Enterobacteriaceae · Carbapenemase · KPC · NDM · Colistin · C. difficile
Multidrug-resistant organisms comprise MRSA (altered PBP2a from mecA; resistant to beta-lactams except ceftaroline; treat with vancomycin, linezolid, or daptomycin), VRE (altered D-Ala-D-Ala; linezolid or daptomycin), ESBL (E. coli and Klebsiella; carbapenems, NEVER piperacillin-tazobactam for bacteraemia per MERINO), and CRE (carbapenemases KPC and NDM; ceftazidime-avibactam for KPC, aztreonam plus CZA for NDM, meropenem-vaborbactam), plus C. difficile (spore, toxin, post-antibiotic). The two pillars are targeted antibiotic therapy and infection control — contact precautions, isolation, hand hygiene (soap-and-water for C. difficile spores), and antimicrobial stewardship. Type the carbapenemase before choosing the novel beta-lactam: KPC and OXA-48 respond to ceftazidime-avibactam, but NDM (a metallo-beta-lactamase) does NOT — use aztreonam plus CZA.
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A 62-year-old man is admitted to your ICU in septic shock from a catheter-related bloodstream infection, repatriated 10 days ago from a three-week hospitalisation in New Delhi for motorcycle trauma. MAP 58 on noradrenaline 0.4 after 30 mL/kg crystalloid, lactate 5.2, creatinine 220. Blood cultures grow Klebsiella pneumoniae resistant to meropenem, imipenem, ertapenem, and every cephalosporin, susceptible only to colistin and tigecycline. His rectal surveillance swab is positive — the European NDM-1 survey found K. pneumoniae the most-reported species and most cases linked to hospital care on the Indian subcontinent.[22]
The single question that decides whether he lives is not "which broad-spectrum agent" — it is which carbapenemase. If it is KPC, ceftazidime-avibactam saves him; if it is NDM (the New Delhi metallo-beta-lactamase, and the geography screams it), avibactam does nothing, and the regimen must be aztreonam plus CZA — the enzyme-to-drug mapping that current ICU guidance is built on. Send the molecular test now, cover both possibilities empirically, and contact-isolate from the moment of suspicion.[24][6]
References28ShowHide
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